1. Field of the Invention
This invention relates to novel platinum complexes having an antitumor effect.
2. Description of the Prior Art
With respect to platinum complexes having an antitumor effect, cis-Platin (cis-dichlorodiammineplatinum) is already available commercially and is being applied to many cases because of its striking effect. Other platinum complexes having an antitumor effect as well are reported in several papers. Of these, platinum complexes having a straight alkyl diamine as a ligand are limited to those having a ligand represented by the general formula EQU H.sub.2 N--C.sub.n R.sub.2n --NH.sub.2 (I)
(wherein R is a hydrogen atom or a substituent such as an alkyl group, a hydroxyl group or the like and n is in an integer of 1 to 3), except for a few complexes described in Inorg. Chem. Acta, 26 (1978) L13-L14. Kidani et al. also described the complexes having the diamine ligand represented by the general formula (II), in U.S. Pat. No. 4,477,387(1984). ##STR4## (wherein R.sub.1 ' and R.sub.2 ' are the same or different and each is hydrogen, an alkyl group or an aryl group, and p is 0 or in an integer of 1 to 3). But, of these, the complexes which have the diamine ligand represented by the general formula (II) wherein p is 2 or 3, were not characterized by any analysis or biological test, at all.
As mentioned above, cis-Platin is commercially available as a platinum complex carcinostatic agent. However, cis-Platin has high renal toxicity, which posses a dose limiting factor. Therefore, in administering cis-Platin, it is requisite that a large amount of water be administered before and during the administration of cis-Platin and that cis-Platin be administered together with a diuretics and over a long period of time. Further, cis-Platin, having low solubility in water and dissolving in water slowly, is supplied at a very low concentration. Furthermore, cis-Platin has very high vomiting toxicity, posing a problem in cure. Because of these drawbacks of cis-Platin, many researches have been conducted in order to find a platinum complex having an antitumor activity which has high solubility in water, low renal toxicity and low vomiting toxicity. However, no platinum complex has been applied practically till now.